Evaluation of the Shallow Gas Hydrate Production Based on the Radial Drilling-Heat Injection-Back Fill Method.

It has been evidenced that shallow gas hydrate resources are abundant in deep oceans worldwide. Their geological background, occurrence, and other characteristics differ significantly from deep-seated hydrates. Because of the high risk of well construction and low production efficiency, they are difficult to be recovered by using conventional oil production methods. As a result, this paper proposes an alternative design based on a combination of radial drilling, heat injection, and backfilling methods. Multi-branch holes are used to penetrate shallow gas hydrate reservoirs to expand the depressurization area, and heat injection is utilized as a supplement to improve gas production. Geotechnical information collected from an investigation site close to the offshore production well in the South China Sea is used to assess the essential components of this plan, including well construction stability and gas production behavior. It demonstrates that the hydraulic fracturing of the 60 mbsf overburden layer can be prevented by regulating the drilling fluid densities. However, the traditional well structure is unstable, and the suction anchor is advised for better mechanical performance. The gas production rate can be significantly increased by combining hot water injection and depressurization methods. Additionally, the suitable production equipment already in use is discussed. [ABSTRACT FROM AUTHOR]